Recently, with a demand of large capacity for a storage system, the number of storage devices installed in the storage system tends to increase. However, there is a problem that the power consumption also increases in the storage system, and therefore, a control technique for power saving has been desired. For example, power saving may be realized such that the installed storage devices are actively caused to transition to a power saving state. As an example of such power saving, a link power management (LPM) technique has been used in which an amount of data input/output into/from a storage device is monitored, and the storage device is caused to transition to a sleep state when an amount of input/output data has become zero.
In addition, a technique described below has been proposed for power saving. For example, a storage controller has been proposed in which supply of power to an unconnected port among two or more ports is stopped (see Japanese National Publication of International Patent Application No. 2012-524928). In addition, for example, it has been proposed that, in a disk device compatible with fibre channel arbitrated loop (FC-AL), an operation of a driver/receiver circuit included in an unused port among two or more ports is stopped (see Japanese Laid-open Patent Publication No. 10-333796).
In the above-described technique in which the storage device is caused to transition to the sleep state in the case where an amount of input/output data has become zero, when an input/output is newly requested for the storage device, the storage device is caused to be recovered from the sleep state. When an input/output is requested for the storage device in the sleep mode as described above, a response speed to the input/output request is reduced compared to the regular state. Thus, in the above-described technique, the power saving of the storage device is realized, but there is a problem in which the access performance of the storage device is reduced.
An object of an embodiment is to provide a storage system, a connection controller, and a storage control program in each of which the access performance is improved.